Enhanced oil recovery, EOR, has been the object of intensive research for the past three decades. Many EOR processes are aimed at recovering more oil from "depleted" reservoirs which still contain as much as 50% or more of the original oil in place. The overall picture of the technological and economical feasibility of EOR processes aimed at recovering more oil from "depleted" reservoirs that has emerged is one of great complexity of the processes, coupled with an uncertainty of achieving enhanced oil recovery at all, let alone in an economical manner. One of the major problems faced by many EOR processes is the possible loss of the chemicals and/or solvents injected, either by adsorption on the rock surface or by channeling and consequent bypassing of the oil to be recovered. In other words, the sweep efficiency of an EOR process may turn out to be far less than expected or desired. Some techniques aimed at permeability and/or mobility control appear to be more promising.
At the present time, crude oil prices have decreased significantly as a result of an "oil glut". Under these conditions, the necessity for EOR processes may be considered unnecessary. However, EOR process are important since:
(i) the world-wide oil shortage of crude existing just a few years ago is likely to reappear before long,
(ii) domestic production in Canada and in the U.S.A. is far from adequate to cover the needs of these countries and, if overseas imports of crude were ever cut off, production would have to be increased by any and all means available at that time, and
(iii) conventional sources of crude oil will gradually run out world-wide and then there will be a tremendous incentive to recover the vast resources of crude which will be still present in the "depleted" reservoirs all over the world.
Certain prior art has come to the attention of the applicant relating to oil recovery procedures as a result of prosecution of the precursor applications, namely:
______________________________________ U.S. 1,093,031 Brown 1,099,170 Dunn 1,252,557 Dunn 1,816,260 Lee 2,171,416 Lee 1,826,371 Spindler 2,335,558 Young 2,725,106 Spearow 3,084,743 West et al 3,123,134 Kyte et al 3,500,914 Petteway 4,171,017 Klass 4,241,787 Price 4,330,306 Salant ______________________________________
Secondary Recovery of Oil in the United States, Published by the American Institute, 1950, pp. 592, 610-614, 623-627.
A variety of procedures are described in this material. The two Lee patents and the two Dunn patents employ the use of pressurized gas to force oil out of depleted formations. Salant, Young, Klass and Price all employ semi-permeable membranes in the separation of oil from gases. Spearow discloses the application of pressure to the top of a formation to cause liquid in flow through a said formation.